Method for producing partially crystalline polyether polyols

ABSTRACT

The present invention relates to a process for the preparation of novel, partially crystalline polyether polyols with a functionality of ≧2, an average molecular weight M n  of 500 to 100,000 and a molar proportion of isotactic triads determining the crystallinity of &gt;28%. The new polyether polyols are prepared by polymerizing alkylene oxides in the presence of a bimetallic :-oxoalkoxide modified with hydroxyl compounds.

BACKGROUND OF THE INVENTION

The invention relates to a process for the preparation of novel,partially crystalline polyether polyols having a hydroxy functionalityof ≧2 and to the new polyether polyols and the use thereof.

It is known from the literature that products with improved mechanicalproperties may be synthesised with crystallising polyether polyols basedon propylene oxide having a functionality of 2 according to theisocyanate-polyaddition process (J. of Polymer Sci. (Polym. Chem. Ed.)Vol. 15, 1655ff (1977)). The preparation of crystallinehydroxyfunctional dihydroxy polyethers from isotactic polypropyleneglycols by ozonolysis followed by hydrogenation with moisture-sensitiveand oxygen-sensitive reagents and fractionation is extremely laboriousand permits little variability. The object was, therefore, to provide abroad range of crystalline hydroxy polyethers having a functionality of≧2 which are suitable, e.g. for PUR synthesis, according to a lesslaborious process with a large potential for variation.

It is also known that bimetallic μ-oxoalkoxides are suitable for thepolymerisation of propylene oxide to crystallising polyether polyolsU.S. Pat. No. 3,432,445, Polym. Preprints 218 (1984)). No references tothe preparation of polyether polyols having a suitable hydroxyfunctionality which are suitable as chain extenders and crosslinkingagents for isocyanate polyaddition can be derived from the publication.

These bimetallic catalysts used for propylene oxide polymerisationcontain monool substituents which are then incorporated in thepolypropylene oxide during the polymerisation process, which leads topolypropylene oxides having a hydroxy functionality well below 2, whichare unsuitable e.g. as chain extenders for the preparation ofpolyurethanes.

Surprisingly, it has now been found that, as a result of reactingbimetallic catalysts with hydroxyl compounds having a functionality of≧2, catalysts are produced which permit the polymerisation of alkyleneoxide to polyether polyols having a functionality of ≧2. The surprisingaspect hereof is that the catalytically active bimetallic startingcompounds which, according to the literature (J. of Polym. Sci.: Part A:Polym. Chem., 24, 1423 (1986)), are sensitive to impurities, are stillactive for alkylene oxide polymerisation after the reaction withhydroxyl compounds, even at temperatures of 100-160° C.

Moreover, it could not have been foreseen that the bimetallic catalysts,which are to be regarded as polyfunctional with respect to hydroxylcompounds, do not crosslink or interconnect in the presence of hydroxylcompounds having a functionality of ≧2, and remain catalytically active.

SUMMARY OF THE INVENTION

The invention relates, therefore, to a process for the preparation ofnovel, partially crystalline polyether polyols having a hydroxyfunctionality of >2, which is characterised in that alkylene oxides arepolymerised in the presence of bimetallic μ-oxoalkoxides correspondingto the formula (I)

(RO)_(x-1)—M₂—O—M₁—O—M₂—(OR)_(x-1)  (I)

wherein

R stands for a C₁-C₁₀ alkyl radical,

M₁ stands for zinc, cobalt, molybdenum, iron, chromium or manganese,

M₂ means aluminium or titanium and

x stands for 3 to 4,

wherein the μ-oxoalkoxides (I) were reacted beforehand with hydroxylcompounds corresponding to the formula (II)

 in which

Q stands for a C_(2-C) ₂₀ alkyl group,

R¹ and R², independently of one another, mean hydrogen or C₁-C₂₀hydrocarbon radicals,

1 and n independently of one another, stand for numbers from 0 to 40,and

y means an integer from 2 to 6.

Suitable bimetallic μ-oxoalkoxides are preferably those in which M₁stands for zinc and M₂ stands for aluminium, x is the number 3 and Rstands for n- and isopropyl and also n-butyl.

The bimetallic μ-oxoalkoxides suitable for use in the process accordingto the invention are well known and described in more detail, forexample, in the U.S. Pat. No. 3,432,445 mentioned above.

Particularly suitable hydroxyl compounds corresponding to formula (II)which are reacted with the bimetallic μ-oxoalkoxides used are those witha functionality of ≧2, preferably 2 to 6, which have an averagemolecular weight of 90 to 6000, preferably 90 to 2000. The averagemolecular weight is determined in the usual way by measuring the OHvalue or by GPC against polystyrene as a comparison.

Hydroxyl compounds corresponding to formula (II) include, in particular,polypropylene glycols, polyethylene glycols, polyethylene oxidepolypropylene oxide block copolymers and random C—O—PO-copolymers, inaddition to the well known low molecular weight polyhydroxyl compounds.Such compounds are described e.g. in Kirk-Othmer (3)1, 754 to 789.

More particularly preferred hydroxyl compounds include:

Butane-1,4-diol, diethylene glycol, dipropylene glycol, tripropyleneglycol, and polypropylene glycols having an M_(n) of 200 to 2000 startedon propylene glycol, butane-1,4-diol, glycerol, triiethylol propane orsorbitol, or copolymers of propylene oxide and ethylene oxide started onethylene glycol, propylene glycol, butane-1,4-diol, glycerol ortrimethylol propane having an M_(n) of 220 to 2000.

The reaction of the bimetallic μ-oxoalkoxide used corresponding toformula (I) with a hydroxyl compound corresponding to formula (II) takesplace in such a way that 1 mole of polyol (II) is mixed with 5.10⁻⁴ to0.6, preferably 1.10⁻³ to 0.3 mole of μ-oxoalkoxide and the mixture isheated for about 0.5 to 10 hours, preferably 2 to 5 hours, at about 100to 150° C., preferably 110 to 130° C.

The reaction mixture is then stirred for a certain period (about 0.5 to5 hours), optionally at a pressure below atmospheric, at elevatedtemperature (about 100 to 150° C.).

The reaction mixture is then diluted with an organic solvent and/ordiluent, e.g. a suitable hydrocarbon such as xylene and/or ligroin,preferably to 80 to 50 wt. %, and the solvent and/or diluent is thendistilled again at reduced pressure (about 0.01 to 1013 mbar).

The bimetallic μ-oxoalkoxide thus modified with the polyols is thenreacted with suitable alkylene oxides for the preparation of thepartially crystalline polyether polyols. The reaction is carried outpreferably at 20 to 200° C., particularly at 80 to 150° C., under normalor elevated pressure up to 20 bar.

Alkylene oxides suitable for such reactions are the well known alkyleneoxides, preferably propylene oxide, 1,2-butylene oxide, epichlorohydrin,alkyl glycidyl ether and mixtures thereof. Propylene oxide and/orethylene oxide is used in preference. Prior to the reaction withalkylene oxides, the modified μ-oxoalkoxide may be diluted with hydroxylcompounds having a functionality of ≧2, preferably with hydroxylcompounds corresponding to formula (II).

The reaction of the modified catalyst with the alkylene oxides may becarried out in bulk or in a suitable inert organic solvent such astoluene, xylene and/or tetrahydrofuran. The concentration and quantityof the solvent is chosen such that good control of the conversionreaction is possible under the given reaction conditions.

The modified bimetallic μ-oxoalkoxide is generally used in quantities of5.10⁻² to 60 mole %, preferably in quantities of 0.1 to 20 mole %, basedon the quantity of the polyether polyol to be prepared.

The new, partially crystalline polyether polyols with a functionality of≧2, preferably 2 to 6, prepared according to the process of theinvention, have average molecular weights M_(n) of 500 to 100,000,preferably 1000 to 10,000, determined by GPC against polystyrene or bymeans of the hydroxyl end group content (OH value), and have a molarproportion of isotactic triads determining the crystallinity of >28%,preferably >33%, determined by ¹³C-NMR spectroscopy.

The present invention also relates, therefore, to the new, partiallycrystalline polyether polyols of the kind described above.

The process according to the invention may be carried out bothcontinuously and batchwise, for example, in a batch or semi-batchprocess.

According to the process of the invention, the crude product is workedup preferably by dissolving the polyether polyol prepared in a solventsuch as toluene, xylene, tetrahydrofuran, ethyl acetate and/or methylenechloride.

The catalyst is then destroyed by acidified water and the reactionproducts are extracted with aqueous acid (<25 wt. %), preferably withwater. Preferably 1 to 2 acid equivalents are used to destroy thecatalyst. Suitable acids include, i.a., hydrochloric acid, phosphoricacid, sulfuric acid, benzoic acid, acetic acid and/or lactic acid. Ofcourse, other acids may also be used.

After intensive shaking with aqueous acid, the excess acid is removed bywashing with water, optionally in the presence of a compound giving analkaline reaction such as sodium bicarbonate. The polyol solutionobtained is separated from the water, dried and the solvent is removed.

The product may be further purified by fractional precipitation undercold conditions from suitable solvents such as, e.g., acetone.

The partially crystalline polyether polyols prepared according to theprocess of the invention are outstandingly suitable for the preparationof polyurethane materials such as PUR elastomers, PUR foams and PURcoatings. The preparation of the above-mentioned PUR materials is wellknown and described, for example, in Kunststoff Handbuch, volume 7, 3rdedition, Carl-Verlag Verlag, 1993.

EXAMPLES

Preparation of a Bimetallic μ-Oxoalkoxide A Based on Zinc and Aluminium

9 g of zinc acetate and 20.4 g of aluminium isopropylate were heated toreflux in 500 ml of decalin and the isopropyl acetate forming wasdistilled over a column.

After no more isopropyl acetate was produced, the solvent was removedfrom the reaction solution and the residue was taken up in 200 ml ofn-heptane. A 0.35 molar solution of di-μ-oxo-[bis(1-methylethyloxy)-aluminium]-zinc was obtained.

Example 1

a. 1.3 g of the bimetallic μ-oxoalkoxide A, dissolved in 10 ml ofheptane, were added to 100 g of a polypropylene glycol with an OH valueof 112 mg KOH/g and stirred for 3 hours at 130° C. under a pressure of0.2 mbar.

10 ml of toluene were then added to the solution and the reactionmixture was stirred for a further 2 hours at 120-130° C. The toluene wasthen distilled off at a pressure substantially below atmospheric and thereaction mixture was heated again for 1 hour at 130° C.

b. The pre-activated polypropylene glycol was then transferred to anautoclave and reacted with 500 g of propylene oxide under a pressure of3 bar and at a temperature of 130 to 140° C. The crude product isdissolved in toluene and 2n hydrochloric acid is added until a pH of <5is obtained, and the mixture is then shaken with water. The product wasthen washed with an aqueous bicarbonate solution for neutralisation. Theorganic phase was separated and dried.

The partially crystalline, waxy product has an OH value of 20 mg KOHW/gand an M_(n) of 5900 according to GPC. The crystalline phase in thepolyether polyol melted at 55° C. The product contained a molarproportion of isotactic triads of 64%.

Example 2

a. 2.7 g of the bimetallic μ-oxoalkoxide A, dissolved in 20 ml ofheptane, were added to 10 g of a propylene glycol with an OH value of515 mg KOH/g and stirred at 130° C. for 5 hours under a pressure of 0.2mbar.

Another 40 g of the polyether with an OH value of 515 were then addedand the reaction mixture was stirred for another 3 hours at 130° C. at apressure below atmospheric.

b. The catalyst solution was transferred to an autoclave and reactedwith 400 g of propylene oxide at a pressure of 3 bar and a temperatureof 130 to 140° C .

The crude product was dissolved in methylene chloride and 20% phosphoricacid was added until a pH of <5 was obtained and the mixture was shakenwith water. The product was washed with an aqueous bicarbonate solutionfor neutralisation. The organic phase was separated and dried.

The partially crystalline, waxy product had an OH value of 65 mg KOH/gand an M_(n) of 1900 according to GPC.

Example 3

a. 5.5 g of the bimetallic μ-oxoalkoxide A, dissolved in 40 ml ofheptane, were added to 100 g of a hydroxypolyether, started ontrimethylol propane, based on propylene oxide with an OH value of 380 mgKOH/g, and stirred at 130° C. for 5 hours under a pressure of 0.2 mbar.

10 ml of toluene were then added to the solution and the reactionmixture was stirred for a further 2 hours at 120-130° C. The toluene wasthen distilled off at a pressure substantially below atmospheric and thereaction mixture was heated again for 1 hour at 130° C.

The catalyst solution was then transferred to an autoclave and reactedwith 1 kg of propylene oxide at a pressure of 3 bar at a temperature of150° C.

The crude product was dissolved in methylene chloride and 2 nhydrochloric acid was added until a pH of <5 was obtained and themixture was then shaken with water. The product was then washed with anaqueous bicarbonate solution for neutralisation. The organic phase wasseparated and dried.

The partially crystalline, waxy product has an OH value of 42 mg KOH/gand an M_(n) of 4290 according to GPC.

Example 4

6.5 g of the bimetallic μ-oxoalkoxide compound A dissolved in 50 g ofn-heptane were added to 500 g of an ethylene oxide-propylene oxidepolyether (50% ethylene oxide) with an OH value of 56 with 70 to 80% ofprimary OH groups and stirred at 130° C. for 3 hours under a pressure of0.2 mbar.

50 ml of toluene were then added to the solution and the reactionmixture was stirred for a further 2 hours at 120 to 130° C. The toluenewas then distilled off at a pressure substantially below atmospheric andthe reaction mixture was heated again for 1 hour at 130° C.

The catalyst solution was then transferred to an autoclave and reactedwith 1500 g of propylene oxide at a pressure of 3 bar at 130 to 140° C.The crude product is dissolved in toluene and 2n hydrochloric acid isadded at pH <5 and the mixture is then shaken with water. The productwas washed with an aqueous bicarbonate solution for neutralisation. Theorganic phase was separated and dried.

The partially crystalline, waxy product has an OH value of 14 and anM_(n) of 7800 according to GPC.

Example 5

1.3 g of the bimetallic μ-oxoalkoxide A dissolved in 10 ml of heptanewere added to 100 g of a polypropylene glycol, started on sorbitol, withan OH value of 450 mg KOH/g and stirred at 130° C. for 3 hours under apressure of 0.2 mbar.

10 ml of toluene were then added to the solution and the reactionmixture was stirred for a further 2 hours at 120 to 130° C. The toluenewas then distilled off at a pressure substantially below atmospheric andthe reaction mixture was heated again for 1 hour at 130° C.

The pre-activated polyol was then reacted with 250 g of propylene oxidein an autoclave under a pressure of 3 bar and at a temperature of 150°C. After the purification stage similar to Example 1b, the partiallycrystalline product has an OH value of 135 mg KOH/g and an M_(n) of 2600according to GPC.

Example 6

1000 g of a polypropylene glycol pre-activated in a similar way toExample 1a, with an OH value of 112 mg KOH/g, were reacted at 120 to130° C. under normal pressure with 1000 g of propylene oxide. The crudeproduct is dissolved in toluene, 150 ml of 2n hydrochloric acid areadded and the mixture shaken with water. The product was washed withaqueous bicarbonate solution for neutralisation.

The organic phase was separated and dried. The partially crystallineproduct has an OH value of 57 mg KOH/g and an M_(n) of 2000 according toGPC.

Example 7

50 ml of toluene were added to 50 g of a polypropylene glycolpre-activated in a similar way to Example 1a, with an OH value of 112 mgKOH/g, and then reacted with 50 g of propylene oxide at 120° C. Afterthe purification stage similar to Example 1b, the viscous product has anOH value of 57.5 mg KOH/g and an M_(n) of 2000 according to GPC.

Example 8

500 g of xylene were added to 250 g of a polypropylene glycolpre-activated in a similar way to Example 1a, with an OH value of 112 mgKOH/g, and then reacted with 750 g of propylene oxide in an autoclave ata pressure of 3 bar and at a temperature of 150° C. After thepurification stage similar to Example 1b, the product which solidifiesat room temperature has an OH value of 32 mg KOH/g and an M_(n) of 3700according to GPC.

What is claimed is:
 1. A process for the preparation of partiallycrystalline polyether polyols having a hydroxy functionality of ≧2,comprising (1) polymerizing (a) an alkylene oxide, with (b) the reactionproduct of (i) one or more bimetallic μ-oxoalkoxides corresponding tothe formula (I): (RO)_(x-1)—M₂—O—M₁—O—M₂—(OR)_(x-1)  (1)  wherein: eachR: independently represents a C₁-C₁₀ alkyl radical; M₁: represents zinc,cobalt, molybdenum, iron, chromium, or manganese; each M₂: independentlyrepresents aluminum or titanium; and each x: independently represents 3or 4; and (ii) one or more hydroxyl compounds corresponding to theformula (II):

 wherein: Q: represents a C₂-C₂₀ alkyl group; R¹ and R²: eachindependently represent a hydrogen atom, or a C₁-C₂₀ hydrocarbonradical; I and n: independently represent numbers of from 0 to 40; andy: represents an integer from 2 to
 6. 2. A process according to claim 1,characterized in that bimetallic μ-oxoalkoxides used are those in whichM₁ stands for zinc and M₂ stands for aluminum, x is the number 3 and Rstands for n-propyl, isopropyl, or n-butyl.
 3. A process according toclaim 1, characterised in that hydroxyl compounds corresponding toformula (II) used are those having a functionality of ≧2 and an averagemolecular weight of 90 to
 6000. 4. A process according to claim 1,characterised in that each 1 mole of the hydroxyl compound correspondingto formula (II) is mixed with 5.10⁻⁴ to 0.6 mole of bimetallicμ-oxoalkoxide.
 5. A process according to claim 1, characterised in thatafter the μ-oxoalkoxides have been mixed with the hydroxyl compounds themixture is heated for 0.5 to 10 hours at 100 to 150° C.